In this study influences of maternal prenatal stress on the cortisol reactions of children to a vaccination were determined. Prenatal stress at around 16 weeks of gestation was measured through questionnaires and a cortisol day curve. Cortisol reactions were determined preceding and following the vaccination. A total of 24 children (age between 3.11 and 5.9 years, mean age 4.9 years) and their mothers participated in this study. Multilevel analysis (hierarchical linear modelling) was used to analyze the data. Children of mothers who had higher concentrations of morning cortisol during pregnancy had higher concentrations of cortisol as compared to children of mothers who had lower concentrations of morning cortisol. Furthermore, more daily hassles and a higher level of fear of bearing a handicapped child during pregnancy were associated with higher concentrations of cortisol in the children.